Boya Jin,1 Aaron Brettin,1 Grant W. Bidneyhttps://orcid.org/0000-0002-9858-2074,1,2 Nicholaos I. Limberopoulos,2 Joshua M. Duran,2 Gamini Ariyawansa,2 Igor Anisimov,2 Augustine M. Urbas,2 Kenneth W. Allen,3 Sarath D. Gunapala,4 Vasily N. Astratov1
1The Univ. of North Carolina at Charlotte (United States) 2Air Force Research Lab. (United States) 3Georgia Institute of Technology (United States) 4Jet Propulsion Lab., CIT (United States)
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Collection of light in photodetector focal plane arrays (FPAs) can be enhanced by microlenses or metasurfaces. We propose an alternative approach based on using microconical waveguide arrays integrated with mid-wave infrared (MWIR) FPAs which allows increasing photon collection efficiency with large angle-of-view (AOV). The light incident on FPA is collected by the wider base of microconical waveguides with diameter (Dt) and delivered to their narrow base with diameter (Db) which is coupled to the photodetector mesa of FPA. A parameter to determine the light-concentrating ability is a power enhancement factor (PEF) defined as the ratio of the powers delivered to the same photodetector with and without the microconical waveguide. By using finite-difference time-domain modeling, the PEF and AOV parameters of the proposed structures are studied as a function of geometrical parameters of microcones. It is demonstrated that the maximal PEFs in excess of 100 require use of sufficiently elongated small-angle microcones with a wavelength-scale diameter of the narrow base. To demonstrate the light concentrating capability, slightly suboptimal microconical arrays with Dt/Db = 60 μm/8 μm and with 150 μm length of microcones were fabricated in photoresist by using a nanoscribe tool directly on top of the front-illuminated Ni/Si Schottky-barrier short-wave infrared photodetectors with 22 μm mesas, and three-time enhancement in the photocurrent response was observed. Due to expected reduction of the thermal noise for compact photodetector mesas, the proposed approach permits increase of the SNR and the operation temperature of the MWIR imaging devices.
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Boya Jin, Aaron Brettin, Grant W. Bidney, Nicholaos I. Limberopoulos, Joshua M. Duran, Gamini Ariyawansa, Igor Anisimov, Augustine M. Urbas, Kenneth W. Allen, Sarath D. Gunapala, Vasily N. Astratov, "Light-harvesting microconical arrays integrated with photodetector FPAs for enhancing infrared imaging devices," Proc. SPIE 12004, Integrated Optics: Devices, Materials, and Technologies XXVI, 120040X (5 March 2022); https://doi.org/10.1117/12.2609883